ABSTRACT Unprecedented nanotechnological advances in recent years hold the promise of revolutionizing many areas of medicine and biology, including cancer diagnostics and treatment. Approximately 90% of all cancer death arise from the metastasis spread of primary tumor. The circulating tumor cell (CTC) counts may be a marker of metastatic development, cancer recurrence, and therapeutic efficacy, which could be used to tailor therapy in order to improve cancer patient survival. However, it might be considered too late to treat patients and, hence, impossible to improve their survival when incurable metastases have already developed by the time of initial diagnosis with existing assays. The goal of this proposal is to develop a novel multifunctional not-toxic gold carbon nanotubes (GNTs) as super-contrast agent for in vivo real-time photoacoustic (PA) detection of CTCs, integrated with their photothermal (PT) treatment. We will pursue this goal through the following Specific Aims. Aim 1. Develop advanced multifunctional hybrid nanoparticles and assess their capability for integrated diagnosis and therapy of cancer at the single-cell level in vitro. Aim 2. Estimate the capability of the integrated PT/PA technique for in vivo detection and therapy of mimic CTCs labeled with GNTs in an animal model. Aim 3. Ascertain the capability of GNTs as PT/PA contrast agents for preclinical monitoring and elimination of CTCs at different stages of tumor development. Specific Aim 4. Determine the clinical capability of PA flow cytometry (PAFC) with novel contrast agents to monitor CTCs in the blood circulation of patients with metastatic tumors. The capability of a painless, non-invasive, PA technique for quantitative detection of CTCs in humans will be assessed in following stages: (1) assessment of healthy volunteer blood in vivo (control) and in vitro alone and spiked with cancer cell lines; and 2) assessment of cancer patient blood at different stages of disease ex vivo; and 3) assessment of cancer patient blood at different stages of disease in vivo. In the course of this study, we will obtain statistically significant data that will demonstrate this innovative technique's unprecedented capability for quantitatively detection and treatment CTCs in vitro and in vivo. The benefits to the public health of achieving this goal extend to routinely monitoring CTCs as early markers for the micrometastasis development and cancer recurrence in vivo in cancer patients, as well as to evaluating the efficacy of radiation, laser and chemotherapy.